Less than 1/3 of snakes are poisonous, and learning how to recognize venomous snakes is beneficial for not just hikers and campers. Due to deforestation and even escaped home pets, poisonous snakes have been found in residential areas.

The best rule when you come upon a snake is ‘STOP’, look around to make sure that is the only one, and determine if it is poisonous. If it is, contact a professional to remove it safely.

Know Your Snakes

Four Kinds. There are four different types of venomous snakes in the United States:[1] cottonmouths, rattlesnakes, copperheads and coral snakes.

Cottonmouths. The cottonmouths have elliptical pupils and range in color from black to green. They have a white stripe along the side of their heads. They are often found in or around water, but have also adapted to live well on land. Young snakes have a bright yellow tail. They are often loners, so if you see multiple snakes coexisting peacefully, it is probably not a cottonmouth.

Rattlesnakes. Look for the rattle on the tail. Some harmless snakes imitate the rattle by brushing their tails through leaves, but only rattle snakes have the button-like rattle at the end of the tail. If you can’t see the rattle, they also have a heavy triangular head and elliptical eyes like a cat.

Copperheads. These beauties have a similar body shape to cottonmouths but are much brighter, ranging from coppery brown to bright orange, silver-pink and peach. The young have yellow tails as well.

Coral snakes. Another beautiful but deadly snake is the Coral snake—so beautiful that other snakes—not-venomous ones such as the King snake—look just like them. They have distinctive coloring, though, with a black, yellow and red bands, a yellow head, and a black band over their nose. One rhyme to help distinguish coral snakes from king snakes is ‘Red touch yellow, kill a fellow. Red touch black, friend to Jack.’ Another variation is ‘Red on black, venom lack; red on yellow, deadly fellow’. However, most of the time coral snakes will not bite – they are very shy. There are no known deaths from the Arizona coral snake and only a few from the Eastern Coral snake.

Look at the color patterns. Venomous Snakes in the U.S. tend to have varying colors. Most snakes that are one solid color are completely harmless. However, some cottonmouths are also venomous so this is not a foolproof way to tell them apart. Also, beware of venomous escaped pets.

Check out their head shape. Non-venomous snakes have a spoon-shaped rounded head and venomous snakes will have a more triangular head.

Look for a rattle. If the snake has a rattle on its tail it is a rattlesnake, and therefore venomous. However, some non-venomous snakes do mimic the rattler by rattling their tails, but lack the rattle “buttons” that sound like little salt shakers.

Look for the heat sensor. Some venomous snakes in the U.S. will have a small depression between the eye and the nostril. This is called a pit (hence “pit viper”), which is used by the snake to sense heat in their prey. Coral snakes are not pit vipers, and lack this feature.

Watch out for mimics. Some non-venomous snakes mimic the patterns and behaviors of venomous snakes. Eastern milk snakes can look like copperheads, rat snakes can look like rattlers, and harmless king snakes can look like coral snakes.

Always treat any snake as a venomous snake if you are uncertain whether it is venomous or non-venomous. And though you should remain cautious, do not kill any snake—it could be illegal to do so, and killing non-venomous snakes allows venomous snake and vermin populations to grow.

Watch how the snake swims. To tell the difference between a venomous water moccasin/cottonmouth and a harmless water snake: Check to see if it is swimming with only its head above water, or whether most of its body is floating, too. If just the head is showing, it is most likely a harmless water snake, but if the body is floating too, it could be a water moccasin (almost all venomous snakes swim with their lungs inflated, leaving the majority of their bodies afloat). Either way, leave it alone.